1. Heat the vegan margarine or oil in a large saucepan over medium heat and then add onions. Saute for about 2 minutes and then add garlic and mushrooms. Saute for a few more minutes until the onions are soft.
2. Add the white wine, Worcestershire sauce, ketchup, nutmeg, and salt and pepper and saute for a few more minutes.
3. Add the seitan and saute for about 2 more minutes. Reduce the heat and add the sour cream into the mushroom and seitan mixture and simmer for 5 to 7 minutes.
4. Serve pasta with "beef" and mushroom stroganoff over top.
You can start prepping the ingredients for this dish and have them ready while the water boils for pasta. If you time things out right, you can saute the onions, garlic, and mushrooms and then drop the pasta into the water. Everything should be done about the same time. This is good comfort food when you feel like having something rich and hearty.
Source of recipe: This recipe was modified from this one from Gen's Guiltless Gourmet: http://foodrecipes.ning.com/page/vegetarian-beef-stroganoff. I modified it slightly by adding more liquid to make it creamier and an ingredient I remember from making beef stroganoff in the past: ketchup.